I. Field of the Invention:
This invention relates generally to alarm systems for indicating to the driver of an emergency vehicle that a second vehicle in its proximity has been alerted to the presence of the emergency vehicle. More particularly, this invention relates to a vehicular alarm and indicator system which is activated by an RF signal generated in the emergency vehicle, so that the occupants of the non-emergency vehicle are made aware of the presence of the emergency vehicle and furthermore, a visual indicator confirms that the RF signal has been received in the non-emergency vehicle. This application is an improvement over my prior U.S. Pat. No. 5,495,243 issued Feb. 27, 1996.
II. Discussion of the Prior Art:
Many modern vehicle passenger compartments are designed and built to be quiet when their windows are closed. Outside noises coming from car horns and radios are prevented from entering the passenger compartment and distracting the driver. Unfortunately, emergency vehicle sirens and train whistles are also prevented from entering the passenger compartment. Car radios or sound systems played at moderate levels inside the vehicle make it even more difficult to hear outside alarms. Thus, an emergency vehicle siren or a train whistle may be undetected by the occupants of a vehicle. In addition, various distractions may be occurring in the vehicle so that the emergency vehicle remains undetected, and this creates a hazardous situation on the highways.
Emergency vehicles need an unobstructed path to respond to an emergency within an acceptable time frame. The occupants of the emergency vehicle need to be able to change traffic signals and alert the drivers of other vehicles to the presence of the emergency vehicle. In the past, radio frequency energy has been used to alert the occupants of one vehicle to the presence of another vehicle. Radio frequency signals were transmitted from one vehicle and detected by an unsuspecting second vehicle. Upon detection, a warning signal was generated in the second vehicle. The warning signal was transmitted over the radio or through independent audio and visual components. This method is shown in U.S. Pat. No. 3,854,119 issued to Friedman et al., and U.S. Pat. No. 3,876,940 issued to Wickford et al. In accordance with the present invention, however, an additional feature is added in that the second vehicle is provided with a signaling light normally rear facing which is activated when the radio frequency signal is detected, thereby permitting the occupants of the emergency vehicle to be aware that its signal has been received.
The Friedman et al. patent describes receiving and identifying amplitude modulated signals to operate switching means for activating devices such as audio speakers, light emitting diodes, panel displays or neon lights in relation to the amplitude of the received signals. The Wickford et al. patent discloses a warning device utilizing radio transmission on an assigned frequency having a transmitter in the emergency vehicle and a receiver in the regular vehicle. One feature of the Wickford et al. patent is the conversion of the received signal to the intermediate frequency of a radio receiver, muting the broadcast reception on the radio or turning the radio on (if it is off), and applying a warning signal through the radio system. In each of these patents, the activating radio frequency energy is transmitted in all directions. Radio frequency energy, however, is not easily blocked by buildings or other objects.
In a rural area, where few emergencies occur and few trains travel, an occasional interruption by a train or emergency vehicle alarm signal may be acceptable. However, in a city or suburban environment, emergencies occur more frequently. Also, the operators and occupants of the emergency vehicle find it helpful to be aware of the fact that the occupants of a second vehicle have been alerted to the presence of the emergency vehicle.
To be useful in cities and suburbs, the energy transmitted by the emergency vehicle's alarm system must be limited to the immediate vicinity. The system should regulate traffic flow by changing traffic signals and alerting the drivers of vehicles to the presence of an emergency vehicle. The present invention satisfies these requirements by utilizing an RF signal of acceptable power wherein the signal is generated and transmitted from an emergency vehicle such as an ambulance, police vehicle, or the like. The RF signal is detectable for a limited distance utilizing a suitable antenna, thereby permitting its use in areas where its detection would otherwise be deemed undesirable.
Light has been used in the past to change traffic signals to accommodate emergency vehicles. One such system is described in U.S. Pat. No. 2,457,502 issued to Shepherd. The Shepherd patent discloses the use of modulated polarized light signals to selectively effect remote control operations by means of light or similar energy. One application described in the Shepherd patent is the use of polarized and modulated light to cause a control mechanism to function and result in the production of a predetermined traffic signal at an intersection. A system much simpler than this for changing traffic signals is currently offered by 3M and includes a high or low priority emitter assembly strobe light and the Opticom.RTM. detector and the traffic signal is changed to allow the emergency vehicle to pass through.
From the above analysis, it can be seen that the prior art references of which we are aware, individually and as a whole, do not disclose an emergency vehicle alarm system utilizing an RF signal to alert the occupants of a possibly unsuspecting vehicle to the presence of the emergency vehicle, and further advising the operator and occupants of the emergency vehicle that the other vehicle has been properly alerted.